As 2013 draws rapidly to a close, I thought the best thing I could post would be the most popular one of all. The most popular post of all since I began writing this blog is Focus and Leverage Part 227. This posting is how I present the Theory of Constraints to people not familiar with it. And since # 228 is the second part of how I do this, I thought I'd finish out the year by posting these two postings. I want to thank everyone for a very remarkable year for my blog. Back in 2010 when I first started posting here, I averaged roughly 1000 page views per month. This month I fully expect the monthly total to be approaching 19,000!! So here are postings 227 and 228 and thank you to everyone. Happy New Year!!!!!
The best way I have found to help people understand just what a constraint is and how it impacts the flow or throughput through a process is by using a simple piping system diagram with each pipe having a different diameter.
In this first slide I simply explain that this is a drawing of a cross section of pipes used to transport water through each section of pipe and into a collection receptacle at the bottom. I then tell them that we need more water flowing and that they have been chosen to fix this system. I emphasize that this system is fed via gravity, so they can’t simply increase the water pressure.
In my next slide, I pose the question that if enough water isn’t flowing through this system, what must they do to make more water flow? Someone in the group will automatically state that in order to have more water flowing through the system, we have to increase the diameter of Section E.
I ask everyone if they understand why they must increase Section E’s diameter and most will answer that they do. For anyone who doesn’t, I simply explain that because of the constricted nature of Section E, water flow is limited at this point. Since they all now have an understanding of this basic concept, I then move to the next slide.
This slide reinforces what I just explained, but then I ask another important question about how large the new diameter should be. In other words, what would this depend upon? What this is supposed to demonstrate is that demand requirements play a role in determining the level of improvement needed to satisfy demand requirements.
In the next slide, I demonstrate the new diameter of Section E and how water is now flowing at a much faster rate than before the diameter change. The important point I emphasize is that the system constraint controls the throughput of water through every section of pipe and if we don't subordinate the rest of the system to the same throughput rate as the constraint, we will automatically have a WIP build-up in front of the constraint.
I then ask the class to identify other physical changes to this system have occurred as a result of our exploitation of the constraint (i.e. increasing the diameter of Section E).
I give them time to answer this question, and most of the time the group will answer correctly. I then post the next slide to reinforce that changes to the system.
I point out that, first and foremost, the system constraint has moved from Section E to Section B. I next explain that the new throughput of water is now governed by the rate that Section B will permit. And finally, I point to the queue of water stacked-up in front of Section B. I now make the point that if the amount of water is still not enough, then we must decide how to exploit the new system constraint and that the process of on-going improvement is continuous.
In my next slide I ask the question, “Would increasing the diameter of any or all other sections have resulted in any more throughput of water through this system?” This question is intended to demonstrate that since the system constraint controls the throughput of a system, focusing improvement anywhere else in the system is usually wasted effort. What I finish with is a before and after slide just to reinforce how things have changed by focusing on the constraint.
Focus and Leverage Part 228
This posting is the second and final piece on how I present the concept of the system constraint in my training material. You will recall in my last posting, we discussed a simple piping diagram with different diameter pipes and that the smallest diameter controlled the throughput of water through the system. In this posting we will expand that thinking to a simple 4-Step process used to make some kind of product. But for anyone new to this blog or the Theory of Constraints, here are Goldratt's 5 Focusing Steps:
1. Identify the system constraint
2. Decide how to exploit the system constraint
3. Subordinate everything else to the system constraint
4. If necessary, elevate the system constraint
5. Return to Step 1, but don't let inertia create a new system constraint
Because I want the class to get the connection from the piping system to the real world, my next slide is the aforementioned simple 4-step process with cycle times for each step listed. I ask the audience to tell me which step is constraining Throughput. It's been my experience that only about 40 % of the class makes the connection between the flow of water through the pipes and the flow of product through this process. What I have found to be very effective is to select someone who does understand the connection explain his or her reasoning. It's important that we don't move on until everyone understands this connection..
I use my next slide to reinforce what their fellow classmates or team members have just explained. I also relate Step 3 of this process to Section E of the piping diagram.
In my next slide, I have the class become consultants who are told that the company who owns this process needs more Throughput. I ask them what would they do and ask them to explain their answers. I usually break the class up into teams and let them discuss this question and that seems to work well.
After the team(s) have explained their plan to improve throughput, I then show them this next slide to reinforce each team's answer on what they would do to increase Throughput.
Because I want the class to understand the negative implications of running each step of this process at maximum capacity, I then ask the class what would happen to the WIP levels if they did.
In the next slide, I demonstrate the impact of trying to maximize the performance metric, efficiency, in each step in the process. The key point here is that the only place where maximizing efficiency makes sense, is in the system constraint. The excessive WIP build-up encumbers the process and extends the cycle time of the process.
I then ask the class, "How fast should each step in this process be running to prevent this excessive build-up of WIP?" This is intended to demonstrate Goldratt's 3rd step, subordination. That is, why it's so important to subordinate every other part of the process to the constraint. This next slide explains, in more detail, the concept of subordination. Steps 1 and 2 must be forced to not outpace the constraint, but must also assure that the constraint is never starved. This slide usually creates an epiphany of sorts for the team or class.
My final slide is one that lists Goldratt's 5 Focusing steps. We talk through each step and relate both the piping diagram and the 4-step process to each of Goldratt's 5 steps.
I have been using this simple method of teaching the concept of the constraint for quite a few years now and it has worked quite well for me. I strongly suggest that you try it yourself.
Bob Sproull
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